The present invention relates generally to a shutter mechanism for automatically opening and closing a port and, in particular, relates to a shutter mechanism which ensures that the sealing/unsealing movement and the rotational movement of a shutter are mutually independent.
The need to control gas or moisture passing through a port is widespread. One specific application where such a requirement is in demand is in analytical instrument, e.g., an infrared spectrophotometer In many analytical instruments a compartment containing the optical elements of the instrument is purged with an inert gas to maintain an optimum ambient for IR transmission a well as to protect the optical surfaces from condensation, contamination or other degrading effects. During such purging the sample compartment is often contaminated by gas or moisture leaks. It is imperative to maintain the sample compartment of an analytical instrument, particularly a sensitive analytical instrument, as clean as possible.
It is known in the art and, in particular, in the analytical instrument field, to seal the ports to the sample compartment during the period of time that the optical compartment is opened or undergoing a purging. This can be accomplished by many mechanisms, such as, for example, sealing the port with tape or with a sponge-like material. However, such techniques provide either insufficient seals or contaminate the sample compartment in and by themselves.
One analytical instrument which is extremely sensitive to the type of problem discussed above is a Fourier Transform Infrared (FT/IR) spectrophotometer. In such an instrument the sample compartment is isolated from the remainder of the instrument except for two ports through which the light beam passes through the sample. Because of the high sensitivity of such a spectrophotometer the cleanliness of the sample compartment is crucially important. To date, conventional techniques used to seal the beam path openings on either side of a sample compartment generally suffer from such difficulties as, for example, short lifetime, failure to seal sufficiently, or the like.